# Bus-voltage selection relay interface

Canonical URL: https://eloragrid.ai/symbols/bus-voltage-selection-relay-interface
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: BSRI
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: substations
Input: Bus measurements and selection status
Output: Selected bus voltage

Selects the voltage measurement associated with the bus supplying the protected circuit.

## In plain English

### What this block does

Selects the voltage measurement associated with the bus supplying the protected circuit.

### A simple example

In a substation bay, one voltage circuit can feed protection while a separately identified winding supplies metering. A voltage-selection circuit must make clear which bus or line measurement is being used. For this reference, the drawing identifies “Bus measurements and selection status” at the input and “Selected bus voltage” at the output. Selection must follow the actual bus configuration.

### What the drawings help you do

Start at the named input: Bus measurements and selection status. Identify its source device or document and the state represented on the drawing. Follow the named output: Selected bus voltage. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Bus measurements and selection status
- Output: Selected bus voltage
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Bus measurements and selection status → BSRI → Selected bus voltage
A reading guide. The entry's original illustration and input/output facts describe this application.

- [Indoor current and voltage transformers](https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers)


## What it represents

Selects the voltage measurement associated with the bus supplying the protected circuit. A voltage-transformer secondary arrangement connects a defined primary voltage measurement to protection, metering or control inputs. Winding identity, fuse protection and the voltage reference must remain visible across the drawing.
In a substation bay, one voltage circuit can feed protection while a separately identified winding supplies metering. A voltage-selection circuit must make clear which bus or line measurement is being used. For this reference, the drawing identifies “Bus measurements and selection status” at the input and “Selected bus voltage” at the output. Selection must follow the actual bus configuration.
Show the primary measurement point, secondary connection, protective devices and relay reference. A missing measurement can resemble a real system disturbance unless the voltage-circuit health is supervised appropriately. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.

## How to read it

- Start at the named input: Bus measurements and selection status. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Selected bus voltage. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Selection must follow the actual bus configuration.
- Show the primary measurement point, secondary connection, protective devices and relay reference. A missing measurement can resemble a real system disturbance unless the voltage-circuit health is supervised appropriately.

## Information to show or reference

- Label the source and connection reference for bus measurements and selection status.
- Identify the destination and defined state of selected bus voltage.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Selection must follow the actual bus configuration.

## Important distinction

Selection must follow the actual bus configuration. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.

## Facts

- Representation: Functional block
- Installation focus: Substations
- Input / boundary: Bus measurements and selection status
- Output / connection: Selected bus voltage
- Lookup label: BSRI is a library lookup label, not a standard device designation.

## Public references

- [Indoor current and voltage transformers](https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers) — ABB. Public technical context for voltage-transformer secondary arrangements. Current and voltage measurement transformers and their secondary interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.